Enhanced color toner images using fluorescing magenta toners

ABSTRACT

A composite color toner image can be enhanced in a printed receiver material by having a separate fluorescing magenta toner image applied over it to provide a “pinkish” fluorescing effect. This separate fluorescing magenta toner image is obtained using visible fluorescing dry magenta toner particles, each of which has a polymeric binder phase and a visible fluorescing colorant that emits at one or more peak wavelengths of from 510 nm and to and including 590 nm. The covering power of the fused visible fluorescing magenta toner particles in the enhanced composite color toner image is at least 350 cm 2 /g to and including 1100 cm 2 /g, and the covering power of each of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles in the enhanced composite color toner image is at least 1500 cm 2 /g to and including 2300 cm 2 /g.

RELATED APPLICATION

This is a divisional application of copending and commonly assigned U.S.Ser. No. 13/462,182 filed May 2, 2012 by Dinesh Tyagi, Louise Granica,and Chung-Hui Kuo (published as US2013/0295498).

FIELD OF THE INVENTION

This invention relates to a method for enhancing color toner imagesusing visible fluorescing magenta toner particles that are applied overthe color toner images.

BACKGROUND OF THE INVENTION

One common method for printing images on a receiver material is referredto as electrophotography. The production of black-and-white or colorimages using electrophotography generally includes the producing alatent electrostatic image by uniformly charging a dielectric membersuch as a photoconductive substance, and then discharging selected areasof the uniform charge to yield an imagewise electrostatic chargepattern. Such discharge is generally accomplished by exposing theuniformly charged dielectric member to actinic radiation provided byselectively activating particular light sources in an LED array or alaser device directed at the dielectric member. After the imagewisecharge pattern is formed, it is “developed” into a visible image usingpigmented or non-pigmented marking particles (generally referred to as“toner particles”) by either using the charge area development (CAD) orthe discharge area development (DAD) method that have an opposite chargeto the dielectric member and are brought into the vicinity of thedielectric member so as to be attracted to the imagewise charge pattern.

Thereafter, a suitable receiver material (for example, a cut sheet ofplain bond paper) is brought into juxtaposition with the toner imagedeveloped with the toner particles in accordance with the imagewisecharge pattern on the dielectric member, either directly or using anintermediate transfer member. A suitable electric field is applied totransfer the toner particles to the receiver material in the imagewisepattern to form the desired print image on the receiver material. Thereceiver material is then removed from its operative association withthe dielectric member and subjected to suitable heat or pressure or bothheat and pressure to permanently fix (also known as fusing) the tonerimage (containing toner particles) to form the desired image on thereceiver material.

Plural toner particle images of, for example, different color tonerparticles respectively, can be overlaid with multiple toner transfers tothe receiver material, followed by fixing of all toner particles to forma multi-color image in the receiver material. Toners that are used inthis fashion to prepare multi-color images are generally Cyan (C),Magenta (M), Yellow (Y), and Black (K) toners containing appropriatedyes or pigments to provide the desired colors or tones.

It is also known to use special spot toners to provide additional colorsthat cannot be obtained by simply mixing the four “primary” toners. Anexample is a specially designed toner that provides a color spot orpearlescent effect.

With the improved print image quality that is achieved with the morerecent electrophotographic technology, print providers and customersalike have been looking for ways to expand the use of images preparedusing electrophotography. Printing processes serve not only to reproduceand transmit objective information but also to convey estheticimpressions, for example, for glossy books or pictorial advertizing.

The desire to provide fluorescing effects has existed for severaldecades and U.S. Pat. No. 3,713,861 (Sharp et al.) describes coating afluorescent material over a document image.

Many color images cannot be reproduced using the traditional CYMK colortoners. Specifically, fluorescing colors or tones cannot be readilyreproduced using the CYMK color toner set. It has been proposed toincorporate fluorescing pigments or dyes into liquid toner particles asdescribed in U.S. Pat. No. 5,105,451 (Lubinsky et al.).

U.S. Patent Application Publication 2010/0164218 (Schulze-Hagenest etal.) describes the use of substantially clear (colorless) fluorescenttoner particles in printing methods over color toner images. Such clearfluorescent toner particles can be used for security purposes since theyare not colored except when excited with appropriate light. Otherinvisible fluorescent pigments for toner images are described in U.S.Pat. No. 6,664,017 (Patel et al.).

Printing processes for providing one or more color toner images areknown, but it is also desired that fluorescing effects can also beprovided for any type of color toner image in order to expand the colorgamut while using conventional non-fluorescing color toners. However, ithas been difficult to properly design desired fluorescing effects usingknown fluorescing colorants (dyes and pigments) as many of them are verysensitive to the illuminating radiation. Further, the color reproductionusing fluorescing color toners produces unrealistically “bright” colorsfor most objects. This is usually an undesirable effect.

When illuminating light has some portion of the electromagnetic spectrumthat is absorbed by fluorescing colorants that emit at a differentwavelength, the overall resulting emissions are very “bright” and mayoverwhelm the non-fluorescing traditional colors in the color tonerimages. This again results in unrealistic images. Other illuminatinglight may not have substantial radiation that is absorbed, and theresulting emission from the fluorescing colorants is quite different. Itis undesirable to have the fluorescing effects depend upon theilluminating light since constantly changing emissions and effects wouldreduce consistency in the resulting color image tone and discouragecustomers from using the fluorescing effects. This is often referred toas illuminant sensitivity and is not a desirable effect.

Cellulosic or paper fibers have a naturally yellow color, and even afterbleaching, the paper fibers can still be too yellow for some receivermaterials. One approach to address this problem is to add a blue dye oroptical brightener to the cellulosic fibers to make the resultingreceiver materials to appear whiter. However, it is difficult to add theappropriate amount of blue dye or optical brightener because the contentof the paper fibers and the environment in which the receiver materialsare used or stored after they are formed, yellowing can increase overtime. As a consequence, there is increased blue emission from thereceiver materials. When human skin tones are printed on such receivermaterials, these unwanted blue emissions give the skin tones a bluishhue. The excessive blue hue from human skin tones will be objectionableto most viewers as the reproductions of the original image will beflawed.

There is a need to expand the possible color gamut with fluorescingeffects without the noted problems.

SUMMARY OF THE INVENTION

This invention provides a method for providing an enhanced toner image,the method comprising:

forming one or more latent images,

developing the one or more latent images with non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner particles, in sequence, to form a composite non-fluorescingcolor toner image,

applying visible fluorescing magenta dry toner particles over thecomposite non-fluorescing color toner image to provide an enhancedcomposite color toner image,

transferring the enhanced composite color toner image to a receivermaterial to form a transferred enhanced composite color toner image, and

fixing the transferred enhanced composite color toner image to thereceiver material,

-   -   wherein each visible fluorescing magenta dry toner particle        consists essentially of a polymeric binder phase and a visible        fluorescing colorant that emits at one or more peak wavelengths        of at least 510 nm and up to and including 590 nm and that is        dispersed within the polymeric binder phase.

In many embodiments, it is advantageous to form a toner image or printsuch that, after fixing, the covering power of the visible fluorescingmagenta dry toner particles in the transferred enhanced composite colortoner image is at least 350 cm²/g to and including 1100 cm²/g, and thecovering power of each of the non-fluorescing cyan, non-fluorescingyellow, non-fluorescing magenta, and non-fluorescing black tonerparticles in the transferred enhanced composite developed color tonerimage is at least 1500 cm²/g to and including 2300 cm²/g.

The method of this invention can be used to provide a printed receivermaterial comprising a printed enhanced composite color toner imagecomprising fused visible fluorescing magenta dry toner particles thatprovide a fluorescing magenta effect printed over non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner images in the printed enhanced composite color toner image.

The visible fluorescing magenta dry toner particles described herein canbe used to provide fluorescing magenta effects in color toner imagesthat do contain non-fluorescing colorants. The desirable effects canhave the appearance of a “pink” or “light magenta” shade of color andthe density of these effects can be varied by changing the lay down ofthe fluorescing magenta dry toner particles as well as the lay down ofthe non-fluorescing color toners.

It is particularly useful to provide fluorescing magenta effects overcomposite three color toner images (for example, CYM) or over four-colortoner images (for example, CYMK). Thus surprisingly new color effectscan open a much wider gamut of color image options for various purposes,and this wider gamut can be identified and defined using various L*,a*,b* color scale designations for identifying colors. Various amounts ofthe visible fluorescing magenta dry toner particles providingfluorescing effects, or various amounts of individual or combinednon-fluorescing color toner images (various color densities) can be usedto expand the options for various fluorescing magenta effects.

In the practice of this invention, when the known composite CYM or CYMKcolor toner images are formed, the addition of the visible fluorescingmagenta dry toner image provides higher chroma images that arereproducible and this effect does not substantially change when theimage is irradiated with illuminating light. It other words, theilluminant sensitivity problem is minimized.

It was also unexpectedly found that when fluorescing magenta colorantsdescribed herein are used that normally exhibit light instability, theiruse in the practice of this invention improved their light stabilitywhen used along with known CYM color toner particles.

It was also observed that the present invention can also minimize aproblem with “blue” hues added to human skin tones because of thepresence of blue dyes or optical brighteners that are commonly added tocellulosic papers. Inexplicably, these undesirable blue skin tone huescan be reduced when the visible fluorescing magenta dry toner particlesare printed over the composite color toner images.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is schematic side elevational view, in cross section, of atypical electrophotographic reproduction apparatus (printer) suitablefor use in the practice of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein to define various components of the visible fluorescingmagenta colorants, polymeric binders, non-fluorescing colorants, andother components, unless otherwise indicated, the singular forms “a”,“an”, and “the” are intended to include one or more of the components(that is, including plurality referents).

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the term'sdefinition should be taken from a standard dictionary.

The use of numerical values in the various ranges specified herein,unless otherwise expressly indicated otherwise, are considered to beapproximations as though the minimum and maximum values within thestated ranges were both preceded by the word “about”. In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as the values within the ranges.In addition, the disclosure of these ranges is intended as a continuousrange including every value between the minimum and maximum values.

The terms “particle size”, “size”, and “sized” as used herein inreference to toner particles including the visible fluorescing magentadry toner particles used in this invention, are defined in terms of themean volume weighted diameter (D_(vol), in μm) as measured byconventional diameter measuring devices such as a Coulter Multisizer(Coulter, Inc.). The mean volume weighted diameter is the sum of themass of visible fluorescing magenta dry toner particle multiplied by thediameter of a spherical particle of equal mass and density, divided bythe total visible fluorescing magenta dry toner particle mass.

“Equivalent circular diameter” (ECD) may be used herein to define thesize (for example, in μm) some particles described herein, and itrepresents the diameter of a circle that has essentially the same areaas a particle projected image when the particle is lying flat to thefield of view. This allows irregularly shaped particles as well asspherical particles to be measured using the same parameter. Techniquesfor measuring ECD are known in the art.

The term “electrostatic printing process” as used herein refers toprinting methods including but not limited to, electrophotography anddirect, solid dry toner printing as described herein. As used in thisinvention, electrostatic printing means does not include the use ofliquid toners to form images on receiver materials.

The term “color” as used herein refers to dry non-fluorescing colortoner particles containing one or more non-fluorescing colorants (dyesor pigments) that provide a color or hue having an optical density of atleast 0.2 at the maximum exposure so as to distinguish them from“colorless” dry toner particles that have a lower optical density. Bynon-fluorescing colorants, it is meant that the colorants do not emitlight or “fluoresce” upon exposure to light of a different wavelength toa significant degree.

The term “visible fluorescing magenta” refers to a colorant, dry tonerparticle, or toner image that provides a color or hue having an opticaldensity of at least 0.2 at the maximum exposure to irradiating light, soas to distinguish them from “colorless” or “substantially clear”fluorescing colorants, toner particles, or toner images as described forexample in U.S. Patent Application Publication 2010/0164218 (notedabove). The “visible fluorescing magenta” colorants and dry tonerparticles emit as one or more peak wavelengths of at least 510 nm and upto and including 590 nm, and particular at one or more peak wavelengthsof at least 520 nm and up to and including 580 nm.

The term “peak wavelength” in reference to the visible fluorescingmagenta colorants in the visible fluorescing magenta dry toner particlesmeans an emission peak within the noted range of wavelengths thatprovides the desired fluorescing magenta effect according to thisinvention. There can be multiple peak wavelengths for a given visiblefluorescing colorant. It is not necessary that the λ_(max) be within thenoted range of wavelengths or that the peak wavelength of interest bethe λ_(max). However, many useful visible fluorescing colorants willhave a λ_(max) within the noted range of wavelengths and this λ_(max)can also be the desired “peak” wavelength.

The term “composite”, when used in reference to developed color tonerimages or developed and fixed color toner images, refers to thecombination of at least 2 (for example, CM) and up to 4 (for example,CYMK), non-fluorescing color toner images in the same multicolor tonerimage.

The term “covering power” refers to the coloring strength (opticaldensity) value of fixed dry toner particles on a specific receivermaterial, or the ability of the fixed dry toner particles to “cover” orhide radiation reflected from the receiver material. For example,covering power values can be determined by making patches of varyingdensities from non-fixed dry toner particles on a receiver material suchas a clear film. The weight and area of each of these patches ismeasured, and the dry toner particles in each patch are fixed forexample in an oven with controlled temperature that is hot enough tomelt the dry toner particles sufficiently to form a continuous thin filmin each patch on the receiver material. The transmission densities ofthe resulting patches of thin films are measured with a Status A bluefilter on an X-rite densitometer (other conventional densitometers canbe used). A plot of the patch transmission densities vs. initial patchdry toner weight is prepared, and the weight per unit area of toner thinfilm is calculated at a transmission density of 1.0. The reciprocal ofthis value, in units of cm²/g of fixed dry toner particles, is the“covering power”. Another way of saying this is that the covering poweris the area of the receiver material that is covered to a transmissiondensity of 1.0 by 1 gram of dry toner particles. As the covering powerincreases, the “yield” of the dry toner particles increases, meaningthat less mass of dry toner particles is needed to create the sameamount of density area coverage in a printed image on the receivermaterial. Thus, covering power is a measurement that is taken after thedry toner particles are fixed (or fused) to a given receiver material. Askilled worker would be able from this description to measure thecovering power of any particular dry toner particle composition(containing polymer binder, colorants, and optional addenda), receivermaterial, and fixing conditions as used in the practice of thisinvention.

Dry Toner Particles

The present invention uses dry toner particles and compositions ofmultiple dry toner particles in dry developers (described below) thatcan be used for reproduction of a fluorescing hue or effect,particularly a visible fluorescing magenta hue that can have theappearance of a “pink” fluorescing hue, by an electrostatic printingprocess, especially by an electrophotographic imaging process.

These visible fluorescing magenta dry toner particles can be porous ornonporous. For example, if they are porous particles, up to 60% of thevolume can be occupied or unoccupied pores within the polymeric binderphase (matrix). The visible fluorescing magenta colorants can be withinthe pores or within the polymeric binder phase. In many embodiments, thevisible fluorescing magenta dry toner particles are not purposelydesigned to be porous although pores may be created unintentionallyduring manufacture. In such “nonporous” embodiments, the porosity of thevisible fluorescing magenta toner particles used in this invention isless than 10% based on the total particle volume within the externalparticle surface, and the visible fluorescing magenta colorants arepredominantly (at least 90 weight %) in the polymeric binder phase.

The visible fluorescing magenta dry toner particles used in thisinvention are generally non-magnetic in that magnetic materials are notpurposely incorporated within the polymeric binder phase.

The visible fluorescing magenta dry toner particles have an externalparticle surface and consist essentially of a polymeric binder phase andone or more visible fluorescing magenta colorants (described below) thatare generally uniformly dispersed within the polymeric binder phase toprovide, when fixed (or fused) and excited by appropriate radiation, thefluorescing magenta effects described herein.

As described in more detail below, these visible fluorescing magenta drytoner particles can be used for imaging in combination withnon-fluorescing dry color toner particles that provide one or morenon-fluorescing colors in a color toner image.

Optional additives (described below) can be incorporated into thevisible fluorescing magenta dry toner particles used in this inventionto provide various properties that are useful for electrostatic printingprocesses. However, only the polymeric binder phase and the visiblefluorescing magenta colorants described herein are essential forproviding the desired fluorescing magenta effects in a fixed color tonerimage and for this purpose, they are the only essential components ofthe visible fluorescing magenta dry toner particles.

The polymeric binder phase is generally a continuous polymeric phasecomprising one or more polymeric binders that are suitable for thevarious imaging methods described herein. Many useful binder polymersare known in the art as being suitable for forming dry toner particlesas they will behave properly (melt and flow) during thermal fixing ofthe toner particles to a suitable receiver material. Such polymericbinders generally are amorphous and each has a glass transitiontemperature (T_(g)) of at least 50° C. and up to and including 100° C.In addition, the visible fluorescing magenta dry toner particlesprepared from these polymeric binders have a caking temperature of atleast 50° C. so that the visible fluorescing magenta dry toner particlescan be stored for relatively long periods of time at fairly hightemperatures without having individual particles agglomerate and clumptogether.

Useful polymeric binders for providing the polymeric binder phaseinclude but are not limited to, polycarbonates, resin-modified malicalkyd polymers, polyamides, phenol-formaldehyde polymers and variousderivatives thereof, polyester condensates, modified alkyd polymers,aromatic polymers containing alternating methylene and aromatic units,and fusible crosslinked polymers.

Other useful polymeric binders are vinyl polymers, such as homopolymersand copolymers derived from two or more ethylenically unsaturatedpolymerizable monomers. For example, useful copolymers can be derivedone or more of styrene or a styrene derivative, vinyl naphthalene,p-chlorostyrene, unsaturated mono-olefins such as ethylene, propylene,butylene, and isobutylene, vinyl halides such as vinyl chloride, vinylbromide, and vinyl fluoride, vinyl acetate, vinyl propionate, vinylbenzoate, vinyl butyrate, vinyl esters such as esters of mono carboxylicacids including acrylates and methacrylates, acrylonitrile,methacrylonitrile, acrylamides, methacrylamide, vinyl ethers such asvinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether, N-vinylindole, N-vinyl pyrrolidone, and others that would be readily apparentto one skilled in the electrophotographic polymer art.

For example, homopolymers and copolymers derived from styrene or styrenederivatives can comprise at least 40 weight % and to and including 100weight % of recurring units derived from styrene or styrene derivatives(homologs) and from 0 to and including 40 weight % of recurring unitsderived from one or more lower alkyl acrylates or methacrylates (theterm “lower alkyl” means alkyl groups having 1 to 6 carbon atoms). Otheruseful polymers include fusible styrene-acrylic copolymers that arepartially crosslinked by incorporating recurring units derived from adivinyl ethylenically unsaturated polymerizable monomer such asdivinylbenzene or a diacrylate or dimethacrylate. Polymeric binders ofthis type are described, for example, in U.S. Reissue Pat. No. 31,072(Jadwin et al.) that is incorporated herein by reference. Mixtures ofsuch polymeric binders can be used if desired.

Some useful polymeric binders are derived from styrene or another vinylaromatic ethylenically unsaturated polymerizable monomer and one or morealkyl acrylates, alkyl methacrylates, or dienes wherein the styrenerecurring units comprise at least 60% by weight of the polymer. Forexample, copolymers that are derived from styrene and either butylacrylate or butadiene are also useful as polymeric binders, or thesecopolymers can be part of blends of polymeric binders. For example, ablend of poly(styrene-co-butyl acrylate) and poly(styrene-co-butadiene)can be used wherein the weight ratio of the first polymeric binder tothe second polymeric binder is from 10:1 to 1:10, or from 5:1 to 1:5.

Styrene-containing polymers are particularly useful and can be derivedfrom one or more of styrene, α-methylstyrene, p-chlorostyrene, and vinyltoluene. Useful alkyl acrylates, alkyl methacrylates, and monocarboxylicacids that can be copolymerized with styrene or styrene derivativesinclude but are not limited to, acrylic acid, methyl acrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, ethyl acrylate, butylacrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylicacid, ethyl methacrylate, butyl methacrylate, and octyl methacrylate.

Condensation polymers are also useful as polymeric binders in thevisible fluorescing magenta dry toner particles. Useful condensationpolymers include but are not limited to, polycarbonates, polyamides,polyesters, polywaxes, epoxy resins, polyurethanes, and polymericesterification products of a polycarboxylic acid and a diol comprising abisphenol. Particularly useful condensation polymeric binders includepolyesters and copolyesters that are derived from one or more aromaticdicarboxylic acids and one or more aliphatic diols, including polyestersderived from isophthalic or terephthalic acid and diols such as ethyleneglycol, cyclohexane dimethanol, and bisphenols (such as Bisphenol A).Other useful polyester binders can be obtained by theco-polycondensation polymerization of a carboxylic acid componentcomprising a carboxylic acid having two or more valencies, an acidanhydride thereof or a lower alkyl ester thereof (for example, fumaricacid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid,trimellitic acid, or pyromellitic acid), using as a diol component abisphenol derivative or a substituted compound thereof. Other usefulpolyesters are copolyesters prepared from terephthalic acid (includingsubstituted terephthalic acid), a bis[(hydroxyalkoxy)phenyl]alkanehaving 1 to 4 carbon atoms in the alkoxy radical and from 1 to 10 carbonatoms in the alkane moiety (that can also be a halogen-substitutedalkane), and an alkylene glycol having from 1 to 4 carbon atoms in thealkylene moiety. Specific examples of such condensation copolyesters andhow they are made are provided for example in U.S. Pat. No. 5,120,631(Kanbayashi et al.), U.S. Pat. No. 4,430,408 (Sitaramiah), and U.S. Pat.No. 5,714,295 (Wilson et al.), all of which are incorporated herein byreference for describing such polymeric binders. A useful polyester is apropoxylated bisphenol—A fumarate.

Useful polycarbonates are described in U.S. Pat. No. 3,694,359 (Merrillet al.) that is incorporated by reference, which polycarbonates cancontain alklidene diarylene moieties in recurring units.

Other specific polymeric binders useful in the visible fluorescingmagenta dry toner particles are described in [0031] of U.S. PatentApplication Publication 2011/0262858 (noted above) that is incorporatedherein by reference.

In some embodiments, the polymeric binder phase comprises a polyester ora vinyl polymer derived at least in part from styrene or a styrenederivative, both of which are described above.

In general, one or more polymeric binders are present in the visiblefluorescing magenta dry toner particles in an amount of at least 50weight % and up to and including 80 weight %, or typically at least 60weight % and up to and including 75 weight %, based on the total visiblefluorescing magenta dry toner particle weight.

The visible fluorescing magenta dry toner particles used in thisinvention are not generally perfectly spherical so it is best to definethem by the mean volume weighted diameter (D_(vol)) that can bedetermined as described above. Before fixing, the D_(vol) can be atleast 4 μm and up to and including 20 μm and typically at least 5 μm andup to and including 12 μm, but larger or smaller particles may be usefulin certain embodiments. Some very small particles can be considered as“liquid” toner particles.

The visible fluorescing magenta colorants useful in the practice of thisinvention can be chosen from any of such pigments and dyes that areknown in the art for emitting at one or more peak wavelengths of atleast 510 nm and up to and including 590 nm, or at least 520 and up toand including 580 nm. Such compounds can be readily determined from suchsources as Honeywell International (New Jersey), Union Pigment(Hongzhau, China), Dayglo Corporation (Ohio), Clariant Corporation(Rhode Island), H. W. Sands (Jupiter Fla.), Sun Chemicals (Ohio), andRisk Reactor (California).

For example, useful visible fluorescing magenta colorant classes arerhodamine, perylene, naphthalimide, and anthrone classes of fluorescingmagenta colorants that emit at one or more peak wavelengths of at least510 nm and up to and including 590 nm, or one or more peak wavelengthsof at least 520 nm and up to and including 590 nm.

Mixtures of two or more of the visible fluorescing magenta colorants asdescribed herein can be used if desired. In some embodiments, one ormore fluorescing magenta colorants can be used in combination with oneor more colorless or visible non-magenta fluorescing colorants.

The one or more visible fluorescing magenta colorants are generallypresent in the visible fluorescing magenta dry toner particles in anamount of at least 0.5 weight % and up to and including 20 weight %, ortypically at least 2 weight % and up to and including 12 weight %, basedon the total visible fluorescing magenta dry toner particle weight.

Various optional additives that can be present in the visiblefluorescing magenta dry toner particles can be added in the dry blend ofpolymeric resin particles and visible fluorescing magenta colorants asdescribed below. Such optional additives include but are not limited to,non-fluorescing colorants (such as dyes and pigments), charge controlagents, waxes, fuser release aids, leveling agents, surfactants,stabilizers, or any combinations of these materials. These additives aregenerally present in amounts that are known to be useful in theelectrophotographic art as they are known to be used in other dry tonerparticles, including dry color toner particles.

In some embodiments, a spacing agent, fuser release aid, flow additiveparticles, or combinations of these materials can be provided on theouter surface of the visible fluorescing magenta dry toner particles,and such materials are provided in amounts that are known in theelectrophotographic art. Generally, such materials are added to thevisible fluorescing magenta dry toner particles after they have beenprepared using the dry blending, melt extrusion, and breaking process(described below).

Inorganic or organic non-fluorescing colorants (pigments or dyes) can bepresent in the visible fluorescing magenta dry toner particles toprovide any suitable color, tone, or hue other than fluorescing magentaeffect described herein. Most visible fluorescing magenta dry tonerparticles used in the practice of this invention are free ofnon-fluorescing colorants (fluoresce to a insubstantial amount at thenoted wavelengths).

Such non-fluorescing colorants can be incorporated into the polymericbinders in known ways, for example by including them in the dry blendsdescribed below. Useful colorants or pigments include but are notlimited to the following compounds unless they are visible fluorescingmagenta colorants: titanium dioxide, carbon black, Aniline Blue, CalcoilBlue, Chrome Yellow, Ultramarine Blue, DuPont Oil Red, Quinoline Yellow,Methylene Blue Chloride, Malachite Green Oxalate, Lamp Black, RoseBengal, Colour Index Pigment Red 48:1, Colour Index Pigment Red 57:1,Colour Index Pigment Yellow 97, Colour Index Pigment Yellow 17, ColourIndex Pigment Blue 15:1, Colour Index Pigment Blue 15:3, phthalocyaninessuch as copper phthalocyanine, mono-chlor copper phthalocyanine,hexadecachlor copper phthalocyanine, Phthalocyanine Blue or Colour IndexPigment Green 7, and quinacridones such as Colour Index Pigment Violet19 or Colour Index Pigment Red 122, and pigments such as HELIOGEN Blue™,HOSTAPERM Pink™, NOVAPERM Yellow™, LITHOL Scarlet™, MICROLITH Brown™,SUDAN Blue™, FANAL Pink™, and PV FAST Blue™. Mixtures of colorants canbe used. Other suitable non-fluorescing colorants are described in U.S.Reissue Pat. No. 31,072 (noted above) and U.S. Pat. No. 4,160,644(Ryan), U.S. Pat. No. 4,416,965 (Sandhu et al.), and U.S. Pat. No.4,414,152 (Santilli et al.), all of which are incorporated herein byreference.

One or more of such non-fluorescing colorants can be present in thevisible fluorescing magenta dry toner particles in an amount of at least1 weight % and up to and including 20 weight %, or typically at least 2to and including 15 weight %, based on total visible fluorescing magentadry toner particle weight, but a skilled worker in the art would knowhow to adjust the amount of colorant so that the desired fluorescingmagenta effect can be obtained when the visible fluorescing magentacolorants are mixed with the non-fluorescing colorants.

The colorants can also be encapsulated using elastomeric resins that areincluded within the visible fluorescing magenta dry toner particles.Such a process is described in U.S. Pat. No. 5,298,356 (Tyagi et al.)that is incorporated herein by reference.

Suitable charge control agents and their use in toner particles are wellknown in the art, as described for example in the Handbook of ImagingMaterials, 2^(nd) Edition, Marcel Dekker, Inc., New York, ISBN:0-8247-8903-2, pp. 180ff and references noted therein. The term “chargecontrol” refers to a propensity of the material to modify thetriboelectric charging properties of the visible fluorescing magenta drytoner particles. A wide variety of charge control agents can be used asdescribed in U.S. Pat. No. 3,893,935 (Jadwin et al.), U.S. Pat. No.4,079,014 (Burness et al.), U.S. Pat. No. 4,323,634 (Jadwin et al.),U.S. Pat. No. 4,394,430 (Jadwin et al.), U.S. Pat. No. 4,624,907(Motohashi et al.), U.S. Pat. No. 4,814,250 (Kwarta et al.), U.S. Pat.No. 4,840,864 (Bugner et al.), U.S. Pat. No. 4,834,920 (Bugner et al.),and U.S. Pat. No. 4,780,553 (Suzuka et al.), all of which areincorporated herein by reference. The charge control agents can betransparent or translucent and free of pigments and dyes. Generally,these compounds are colorless or nearly colorless. Mixtures of chargecontrol agents can be used. A desired charge control agent can be chosendepending upon whether a positive or negative charging visiblefluorescing magenta dry toner particle is needed.

Examples of useful charge control agents include but are not limited to,triphenylmethane compounds, ammonium salts, aluminum-azo complexes,chromium-azo complexes, chromium salicylate organo-complex salts,azo-iron complex salts, an azo-iron complex salt such as ferrate (1-),bis[4-[5-chloro-2-hydroxyphenyl)azo]-3-hydroxy-N-phenyl-2-naphthalene-carboxamidato(2-)],ammonium, sodium, or hydrogen (Organoiron available from HodogayaChemical Company Ltd.). Other useful charge control agents include butare not limited to, acidic organic charge control agents such as2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one (MPP) and derivatives ofMPP such as2,4-dihydro-5-methyl-2-(2,4,6-trichlorophenyl)-3H-pyrazol-3-one,2,4-dihydro-5-methyl-2-(2,3,4,5,6-pentafluorophenyl)-3H-pyrazol-3-one,2,4-dihydro-5-methyl-2-(2-trifluoromethylphenyl)-3H-pyrazol-3-one andthe corresponding zinc salts derived therefrom. Other examples includecharge control agents with one or more acidic functional groups, such asfumaric acid, malic acid, adipic acid, terephthalic acid, salicylicacid, fumaric acid monoethyl ester, copolymers derived from styrene andmethacrylic acid, copolymers of styrene and lithium salt of methacrylicacid, 5,5′-methylenedisalicylic acid, 3,5-di-t-butylbenzoic acid,3,5-di-t-butyl-4-hydroxybenzoic acid, 5-t-octylsalicylic acid,7-t-butyl-3-hydroxy-2-napthoic acid, and combinations thereof. Stillother acidic charge control agents which are considered to fall withinthe scope of the invention include N-acylsulfonamides, such as,N-(3,5-di-t-butyl-4-hydroxybenzoyl)-4-chlorobenzenesulfonamide and1,2-benzisothiazol-3(2H)-one 1,1-dioxide. Another class of chargecontrol agents include, but are not limited to, iron organo metalcomplexes such as organo iron complexes, for example T77 from Hodogaya.Still another useful charge control agent is a quaternary ammoniumfunctional acrylic polymer.

Other useful charge control agents include alkyl pyridinium halides suchas cetyl pyridinium halide, cetyl pyridinium tetrafluoroborates,quaternary ammonium sulfate, and sulfonate charge control agents asdescribed in U.S. Pat. No. 4,338,390 (Lu Chin) that is incorporatedherein by reference, stearyl phenethyl dimethyl ammonium tosylates,distearyl dimethyl ammonium methyl sulfate, and stearyl dimethylhydrogen ammonium tosylate.

One or more charge control agents can be present in the visiblefluorescing magenta dry toner particles in an amount to provide aconsistent level of charge of at least −40 μCoulomb/g to and including−5 μCoulomb/g, when charged. Examples of suitable amounts include atleast 0.1 weight % to and including 10 weight %, based on the totalvisible fluorescing magenta dry toner particle weight.

Useful waxes (can also be known as lubricants) that can be present inthe visible fluorescing magenta dry toner particles include lowmolecular weight polyolefins (polyalkylenes) such as polyethylene,polypropylene, and polybutene, such as Polywax 500 and Polywax 1000waxes from Peterolite, Clariant PE130 and Licowax PE190 waxes fromClariant Chemicals, and Viscol 550 and Viscol 660 waxes from Sanyo. Alsouseful are ester waxed that are available from Nippon Oil and Fat underthe WE-series. Other useful waxes include silicone resins that can besoftened by heating, fatty acid amides such as oleamide, erucamide,ricinoleamide, and stearamide, vegetable waxes such as carnauba wax,rice wax, candelilla wax, Japan wax, and jojoba wax, animal waxes suchas bees wax, mineral and petroleum waxes such as montan wax, ozocerite,ceresine, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax,and modified products thereof. Irrespective to the origin, waxes havinga melting point in the range of at least 30° C. and up to and including150° C. are useful. One or more waxes can be present in an amount of atleast 0.1 weight % and up to and including 20 weight %, or at least 1weight % and up to and including 10 weight %, based on the total visiblefluorescing magenta dry toner particle weight. These waxes, especiallythe polyolefins, can be used also as fuser release aids. In someembodiments, the fuser release aids are waxes having 70% crystallinityas measured by differential scanning calorimetry (DSC).

In general, a useful wax has a number average molecular weight (M_(n))of at least 500 and up to and including 7,000. Polyalkylene waxes thatare useful as fuser release aids can have a polydispersity of at least 2and up to and including 10 or typically of at least 3 and up to andincluding 5. Polydispersity is a number representing the weight averagemolecular weight (M_(w)) of the polyalkylene wax divided by its numberaverage molecular weight (M_(n)).

Useful flow additive particles that can be present inside or on theouter surface of the visible fluorescing magenta dry toner particlesinclude but are not limited to, a metal oxide such as hydrophobic fumedsilica particles. Alternatively, the flow additive particles can be bothincorporated into the visible fluorescing magenta dry toner particlesand on their outer surface. In general, such flow additive particleshave an average equivalent spherical diameter (ESD) of at least 5 nm andare present in an amount of at least 0.01 weight % and up to andincluding 10 weight %, based on the total visible fluorescing magentadry toner particle weight.

Surface treatment agents can also be on the outer surface of the visiblefluorescing magenta dry toner particles in an amount sufficient topermit the visible fluorescing magenta dry toner particles to bestripped from carrier particles in a dry two-component developer byelectrostatic forces associated with the charged image or by mechanicalforces. Surface fuser release aids can be present on the outer surfaceof the visible fluorescing magenta dry toner particles in an amount ofat least 0.05 weight % to and including 1 weight %, based on the totaldry weight of visible fluorescing magenta dry toner particles. Thesematerials can be applied to the outer surfaces of the visiblefluorescing magenta dry toner particles using known methods for exampleby powder mixing techniques.

Spacing treatment agent particles (“spacer particles”) can be attachedto the outer surface by electrostatic forces or physical means, or both.Useful surface treatment agents include but are not limited to, silicasuch as those commercially available from Degussa as R972 and RY200 orfrom Wasker as H2000. Other suitable surface treatment agents includebut are not limited to, titania, aluminum, zirconia, or other metaloxide particles, and polymeric beads all generally having an ECD of lessthan 1 μm. Mixture of these materials can be used if desired, forexample a mixture of hydrophobic silica and hydrophobic titaniaparticles.

Preparation of Dry Toner Particles

The visible fluorescing magenta dry toner particles used in the practiceof this invention can be prepared using any suitable manufacturingprocedure wherein colorants are incorporated within the particles. Suchmanufacturing methods include but are not limited to, melt extrusionmethods, coalescence, spray drying, and other chemical techniques. Thevisible fluorescing magenta dry toners can be prepared as “chemicallyprepared toners”, “polymerized toners”, or “in-situ toners”. They can beprepared using controlled growing instead of grinding. Various chemicalprocesses include suspension polymers, emulsion aggregation,micro-encapsulation, dispersion, and chemical milling. Details of suchprocesses are described for example in the literature cited in [0010] ofU.S. Patent Application Publication 2010/0164218 (Schulze-Hagenest etal.) that is incorporated herein by reference. Such dry toner particlescan also be prepared using limited coalescence process as described inU.S. Pat. No. 5,298,356 (Tyagi et al.) that is incorporated herein byreference, or a water-in-oil-in-water double emulsion process asdescribed in U.S. Patent Application Publication 2011/0262858 (Nair etal.) that is incorporated herein by reference, especially if porosity isdesired in the visible fluorescing magenta dry toner particles. Anothermethod for preparing visible fluorescing magenta dry toner particles isby a spray/freeze drying technique as described in U.S. PatentApplication Publication 2011/0262654 (Yates et al.).

In a particularly useful manufacturing method, a desired polymer binder(or mixture of polymeric binders) for use in the visible fluorescingmagenta dry toner particles is produced independently using a suitablepolymerization process known in the art. The one or more polymericbinders are dry blended or mixed as polymeric resin particles withvisible fluorescing magenta colorants (pigments or dyes) to form a dryblend. The optional additives, such as charge control agents, waxes,fuser release aids, and colorants are also incorporated into the dryblend with the two essential components. The amounts of the essentialand optional components can be adjusted in the dry blend in a suitablemanner that a skilled worker would readily understand to provide thedesired amounts in the resulting visible fluorescing magenta dry tonerparticles. The conditions for mechanical dry blending are known in theart.

For example, the method can comprise dry blending the resin particleswith the visible fluorescing magenta colorant(s), such as the rhodamineclass fluorescing colorants described above, and a charge control agent,and optionally with a wax or colorant, or any combination of theseoptional components, to form a dry blend. The dry blend can be preparedby mechanically blending the components for a suitable time to obtain auniform dry mix.

The dry blend is then melt processed in a suitable apparatus such as atwo-roll mill or hot-melt extruder. In some embodiments, the dry melt isextruded under low shear conditions in an extrusion device to form anextruded composition. However, these low shear conditions are not alwaysrequired in the practice of this invention. The melt processing time canbe from 1 minute to and including 60 minutes, and the time can beadjusted by a skilled worker to provide the desired melt processingtemperature and uniformity in the resulting extruded composition.

For example, it is useful to melt extrude a dry blend of the notedcomponents that has a viscosity of at least 90 pascals sec to andincluding 2300 pascals sec, or typically of at least 150 pascals sec toand including 1200 pascals sec.

Generally, the dry blend is melt extruded in the extrusion device at atemperature higher than the glass transition temperature of the one ormore polymeric binders used to form the polymeric binder phase, andgenerally at a temperature of at least 90° C. and up to and including240° C. or typically of at least 120° C. and up to and including 160° C.The temperature results, in part, from the frictional forces of the meltextrusion process.

The resulting extruded composition (sometimes known as a “melt product”or a “melt slab”) is generally cooled, for example, to room temperature,and then broken up (for example pulverized) into visible fluorescingmagenta dry toner particles having the desired D_(vol) as describedabove. It is generally best to first grind the extruded compositionprior to a specific pulverizing operation. Grinding can be carried outusing any suitable procedure. For example, the extruded composition canbe crushed and then ground using for example a fluid energy or jet millas described for example in U.S. Pat. No. 4,089,472 (Seigel et al.). Theparticles are then further reduced in size by using high shearpulverizing devices such as a fluid energy mill, and then classified asdesired.

The resulting visible fluorescing magenta dry toner particles can thenbe surface treated with suitable hydrophobic flow additive particleshaving an equivalent circular diameter (ECD) of at least 5 nm to affixsuch hydrophobic flow additive particles on the outer surface of theparticles. These hydrophobic flow additive particles can be composed ofmetal oxide particles such as hydrophobic fumed oxides such as silica,alumina, or titania in an amount of at least 0.01 weight % and up to andincluding 10 weight % or typically at least 0.1 weight % and up to andincluding 5 weight %, based on the total visible fluorescing magenta drytoner particle weight.

In particular, a hydrophobic fumed silica such as R972 or RY200 (fromNippon Aerosil) can be used for this purpose, and the amount of thefumed silica particles can be as noted above, or more typically at least0.1 weight % and up to and including 3 weight %, based on the totalvisible fluorescing magenta dry toner particle weight.

The hydrophobic flow additive particles can be added to the outersurface of the visible fluorescing magenta dry toner particles by mixingboth types of particles in an appropriate mixer.

The resulting treated visible fluorescing magenta dry toner particlescan be classified (sieved) through a 230 mesh vibratory sieve to removenon-attached silica particles and silica agglomerates and any othercomponents that may not have been incorporated into the visiblefluorescing magenta dry toner particles. The temperature during thesurface treatment can be controlled to provide the desired attachmentand blending.

Non-fluorescing dry color toner particles useful in the practice of thisinvention can be prepared in various ways as described above, includingthe melt extrusion processes described above for the visible fluorescingmagenta dry toner particles.

The various non-fluorescing dry color toner particles can be preparedusing a suitable polymeric binder phase comprising one or more polymericbinders (as described above) and one or more of non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, or non-fluorescingblack colorants. For example, such colorants can be in principle any ofthe colorants described in the Colour Index, Vols. I and II, 2^(nd)Edition (1987) or in the Pantone® Color Formula Guide, 1^(st) Edition,2000-2001. The choice of particular non-fluorescing colorants for thecyan, yellow, magenta, and black (CYMK) color toners is well describedin the art, for example in the proceedings of IS&T NIP 20: InternationalConference on Digital Printing Technologies, IS&T: The Society forImaging Science and Technology, 7003 Kilworth Lane, Springfield, Va.22151 USA ISBM: 0-89208-253-4, p. 135. Carbon black is generally usefulas the black toner colorant while other colorants for the CYM colortoners include but are not limited to, red, blue, and green pigments,respectively. Specific colorants can include copper phthalocyanine andPigment Blue that can be obtained as Lupreton Blue™ SE1163. Othercolorants useful in non-fluorescing dry color toners are also describedabove as non-fluorescing colorants for the visible fluorescing magentadry toner particles.

The amount of one or more non-fluorescing colorants in thenon-fluorescing dry color toners can vary over a wide range and askilled worker in the art would know how to pick the appropriate amountfor a given non-fluorescing colorant or mixture of colorants. Ingeneral, the total non-fluorescing colorants in each non-fluorescing drycolor toner can be at least 1 weight % and up to and including 40 weight%, or typically at least 3 weight % and up to and including 25 weight %,based on the total dry color toner weight. The non-fluorescing colorantin each non-fluorescing dry color toner can also have the function ofproviding charge control, and a charge control agent (as describedabove) can also provide coloration. All of the optional additivesdescribed above for the visible fluorescing magenta dry toner particlesused in this invention can likewise be used in the non-fluorescing drycolor toners.

Developers

The visible fluorescing magenta dry toner particles used in thisinvention can be used as a dry mono-component developer, or combinedwith carrier particles to form dry two-component developers. In all ofthese embodiments, a plurality (usually thousands or millions) ofindividual visible fluorescing magenta dry toner particles are usedtogether.

Such dry mono-component or dry two-component developers generallycomprise a charge control agent, wax, lubricant, fuser release aid, orany combination of these materials within the visible fluorescingmagenta dry toner particles, or they can also include flow additiveparticles on the outer surface of the particles. Such components aredescribed above.

Useful dry one-component developers generally include the visiblefluorescing magenta dry toner particles as the essential component. Drytwo-component developers generally comprise carrier particles (alsoknown as carrier vehicles) that are known in the electrophotographic artand can be selected from a variety of materials. Carrier particles canbe uncoated carrier core particles (such as magnetic particles) and coremagnetic particles that are overcoated with a thin layer of afilm-forming polymer such as a silicone resin type polymer,poly(vinylidene fluoride), poly(methyl methacrylate), or mixtures ofpoly(vinylidene fluoride) and poly(methyl methacrylate).

The amount of visible fluorescing magenta dry toner particles in atwo-component developer can be at least 4 weight % and up to andincluding 20 weight % based on the total dry weight of the two-componentdry developer.

Image Formation Using Visible Fluorescing Magenta Dry Toner Particles

The visible fluorescing magenta dry toner particles used in thisinvention can be applied to a suitable receiver material (or substrate)of any type using various methods such as a digital printing processsuch as an electrostatic printing process, or electrophotographicprinting process as described in L. B. Schein, Electrophotography andDevelopment Physics, 2^(nd) Edition, Laplacian Press, Morgan Hill,Calif., 1996 (ISBN 1-885540-02-7), or by an electrostatic coatingprocess as described for example in U.S. Pat. No. 6,342,273 (Handels etal.) that is incorporated herein by reference.

Such receiver materials include, but are not limited to, coated oruncoated papers (cellulosic or polymeric papers), transparent polymericfilms, ceramics, paperboard, cardboard, metals, fibrous webs or ribbons,and other substrate materials that would be readily apparent to oneskilled in the art. In particular, the receiver materials (also known asthe final receiver material or final receiver material) can be sheets ofpaper or polymeric films that are fed from a supply of receivermaterials. It is particularly useful to apply the toner images accordingto this invention to cellulosic (paper) receiver materials containingblue dyes or optical brighteners.

For example, the visible fluorescing magenta dry toner particles can beapplied to a receiver material by a digital printing process such as anelectrostatic printing process that includes but is not limited to, anelectrophotographic printing process, or by a coating process such as anelectrostatic coating process including an electrostatic brush coatingas described in U.S. Pat. No. 6,342,273 (noted above).

In one electrophotographic method, one or more latent images (that is anelectrostatic latent image) can be formed on a primary imaging membersuch as a charged photoconductor belt or roller using a suitable lightsource such as a laser or light emitting diode. The one or more latentimages are then developed on the primary imaging member by bringing thelatent images into close proximity with a dry one-component or drytwo-component developer comprising the visible fluorescing magenta drytoner particles described herein to form a visible fluorescing magentadry toner image on the primary imaging member.

In the embodiments of multi-color printing, multiple photoconductors canbe used, each developing a separate non-fluorescing color dry tonerimage and another for developing the visible fluorescing magenta drytoner image. Alternatively, a single photoconductor can be used withmultiple developing stations where after each latent non-fluorescingimage and visible fluorescing magenta toner image is developed, it istransferred to the receiver material, or it is transferred to anintermediate transfer member (belt or rubber) and then to the receivermaterial after all of the toner images have been accumulated on theintermediate transfer member.

In some embodiments, it is desirable to develop and fix the latent imagewith sufficient dry toner particles to form an enhanced compositenon-fluorescing developed color toner image wherein the covering powerof the visible fluorescing dry magenta toner particles in the enhancedcomposite non-fluorescing developed color toner image is at least 350cm²/g to and including 1100 cm²/g, and the covering power of each of thenon-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta,and non-fluorescing black toner particles in the enhanced compositenon-fluorescing developed color toner image is at least 1500 cm²/g toand including 2300 cm²/g.

In more particular embodiments, the covering power of the visiblefluorescing magenta dry toner particles in the enhanced compositenon-fluorescing developed color toner image is at least 400 cm²/g to andincluding 600 cm²/g, and the covering power of each of thenon-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta,and non-fluorescing black toner particles in the enhanced compositenon-fluorescing developed color toner image is at least 1700 cm²/g toand including 2100 cm²/g.

In some of these embodiments, the visible fluorescing magenta dry tonerparticles comprise a rhodamine class fluorescing colorant that has atleast one peak wavelength of at least 520 nm and up to and including 590nm, that is present in an amount of at least 0.5 weight % and up to andincluding 10 weight %, based on the total visible fluorescing magentatoner particle weight.

While a developed dry toner image can be transferred to a final receiver(receiver material) using a thermal or thermal assist process as isknown in the art, it is generally transferred using an electrostaticprocess including an electrophotographic process such as that describedin L. B. Schein, Electrophotography and Development Physics, 2^(nd)Edition, Laplacian Press, Morgan Hill, Calif., 1996. The electrostatictransfer can be accomplished using a corona charger or an electricallybiased transfer roller to press the receiver material into contact withthe primary imaging member while applying an electrostatic field. In analternative embodiment, a developed toner image can be first transferredfrom the primary imaging member to an intermediate transfer member (beltor roller) that serves as a receiver material, but not as the finalreceiver material, and then transferred from the intermediate transfermember to the final receiver material.

Electrophotographic color printing generally includes subtractive colormixing wherein different printing stations in a given apparatus areequipped with non-fluorescing cyan, non-fluorescing yellow,non-fluorescing magenta, and non-fluorescing black toner particles.Thus, a plurality of toner images of different non-fluorescing colorscan be applied to the same primary imaging member (such as dielectricmember), intermediate transfer member, and final receiver material,including one or more non-fluorescing color toner images in combinationwith the toner image comprising the visible fluorescing magenta drytoner particles described herein. Such different toner images aregenerally applied or transferred to the final receiver material in adesired sequence or succession using successive toner application orprinting stations as described below.

The various transferred toner images are then fixed (thermally fused) onthe receiver material in order to permanently affix them to the receivermaterial. This fixing can be done using various means such as heatingalone (non-contact fixing) using an oven, hot air, radiant, or microwavefusing, or by passing the toner image(s) through a pair of heatedrollers (contact fixing) to thereby apply both heat and pressure to thetoner image(s) containing toner particles. Generally, one of the rollersis heated to a higher temperature and can have an optional release fluidto its surface. This roller can be referred to as the fuser roller, andthe other roller is generally heated to a lower temperature and usuallyserves the function of applying pressure to the nip formed between therollers as the toner image(s) is passed through. This second roller canbe referred to as a pressure roller. Whatever fixing means is used, thefixing temperature is generally higher than the glass transitiontemperature of the various toner particles, which T_(g) can be at least45° C. and up to and including 90° C. or at least 50° C. and up to andincluding 70° C. Thus, fixing is generally at a temperature of at least95° C. and up to and including 220° C. or more generally at atemperature of at least 135° C. and up to and including 210° C.

As the developed toner image(s) on the receiver material is passedthrough the nip formed between the two rollers, the various fluorescingand non-fluorescing dry toner particles in the developed toner image(s)are softened as their temperature is increased upon contact with thefuser roller. The melted toner particles generally remain affixed on thesurface of the receiver material.

For example, the method of this invention can comprise:

forming a non-fluorescing cyan, non-fluorescing yellow, non-fluorescingmagenta, and non-fluorescing black dry toner images, in sequence, in acomposite non-fluorescing color image on a receiver material,

then forming the visible fluorescing magenta dry toner image, over thecomposite non-fluorescing color toner image, and

fixing both the composite non-fluorescing color toner image and thevisible fluorescing magenta dry toner image to the receiver material.

It is advantageous that the present invention can be used in a printingapparatus with multiple printing stations, for example where the visiblefluorescing magenta dry toner particles can be applied to a receivermaterial at the last or first printing station, over the compositenon-fluorescing color toner image.

Certain embodiments of the invention where multiple color toner imagesare printed along with the visible fluorescing magenta dry toner imagecan be achieved using a printing machine that incorporates at least fiveprinting stations or printing units. For example, the printing methodcan comprise forming composite non-fluorescing cyan (C), yellow (Y), andmagenta (M) toner images, or composite non-fluorescing cyan (C), yellow(Y), magenta (M), and black (K) toner images, and the visiblefluorescing magenta toner image is formed last, on the receiver materialusing at least five sequential toner stations in a colorelectrophotographic printing machine.

A useful printing machine is illustrated in FIG. 1 of the presentapplication. FIG. 1 is a side elevational view schematically showingportions of a typical electrophotographic print engine or printerapparatus suitable for printing of one or more toner images. Anelectrophotographic printer apparatus 100 has a number of sequentiallyarranged electrophotographic image forming printing modules M1, M2, M3,M4, and M5. Each of the printing modules generates a single dry tonerimage for transfer to a receiver material successively moved through themodules. Each receiver material, during a single pass through the fivemodules, can have transferred in registration thereto up to five singletoner images. A composite color toner image formed on a receivermaterial can comprise combinations or subsets of the CYMK color tonerimages and the visible fluorescing magenta dry toner particles describedherein, on the receiver material over the composite color toner image onthe receiver material. In a particular embodiment, printing module M1forms black (K) toner color separation images, M2 forms yellow (Y) tonercolor separation images, M3 forms magenta (M) toner color separationimages, and M4 forms cyan (C) toner color separation images. Printingmodule M5 can form the visible fluorescing magenta toner image thatprovides enhancement of the composite color toner image.

Receiver materials 5 as shown in FIG. 1 are delivered from a papersupply unit (not shown) and transported through the printing modulesM1-M5. The receiver materials are adhered [for example electrostaticallyusing coupled corona tack-down chargers (not shown)] to an endlesstransport web 101 entrained and driven about rollers 102 and 103.

Each of the printing modules M1-M5 includes a photoconductive imagingroller 111, an intermediate transfer roller 112, and a transfer backuproller 113, as is known in the art. For example, at printing module M1,a particular toner separation image can be created on thephotoconductive imaging roller 111, transferred to intermediate transferroller 112, and transferred again to a receiver member 5 moving througha transfer station, which transfer station includes intermediatetransfer roller 112 forming a pressure nip with a corresponding transferbackup roller 113.

A receiver material can sequentially pass through the printing modulesM1 through M5. In each of the printing modules a toner separation imagecan be formed on the receiver material 5 to provide the desired enhancedcomposite color toner image described herein.

Printing apparatus 100 has a fuser of any well known construction, suchas the shown fuser assembly 60 using fuser rollers 62 and 64. Eventhough a fuser 60 using fuser rollers 62 and 64 is shown, it is notedthat different non-contact fusers using primarily heat for the fusingstep can be beneficial as they can reduce compaction of toner layersformed on the receiver material 5, thereby enhancing tactile feel.

A logic and control unit (LCU) 230 can include one or more processorsand in response to signals from various sensors (CONT) associated withthe electrophotographic printer apparatus 100 provides timing andcontrol signals to the respective components to provide control of thevarious components and process control parameters of the apparatus asknown in the art.

Although not shown, the printer apparatus 100 can have a duplex path toallow feeding a receiver material having a fused toner image thereonback to printing modules M1 through M5. When such a duplex path isprovided, two sided printing on the receiver material or multipleprinting on the same side is possible.

Operation of the printing apparatus 100 will be described. Image datafor writing by the printer apparatus 100 are received and can beprocessed by a raster image processor (RIP), which can include a colorseparation screen generator or generators. The image data includeinformation to be formed on a receiver material, which information isalso processed by the raster image processor. The output of the RIP canbe stored in frame or line buffers for transmission of the colorseparation print data to each of the respective printing modules M1through M5 for printing color separations in the desired order. The RIPor color separation screen generator can be a part of the printerapparatus or remote therefrom. Image data processed by the RIP can atleast partially include data from a color document scanner, a digitalcamera, a computer, a memory or network. The image data typicallyinclude image data representing a continuous image that needs to bereprocessed into halftone image data in order to be adequatelyrepresented by the printer.

While these embodiments refer to a printing machine comprising five setsof single toner image producing or printing stations or modules arrangedin tandem (sequence), a printing machine can be used that includes moreor less than five printing stations to provide an enhanced compositecolor toner image on the receiver material with five different tonerimages. Useful printing machines also include other electrophotographicwriters or printer apparatus.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A method for providing an enhanced toner image, the methodcomprising:

forming one or more latent images,

developing the one or more latent images with non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner particles, in sequence, to form a composite non-fluorescingdeveloped color toner image,

applying visible fluorescing magenta toner particles over the compositenon-fluorescing developed color toner image to provide an enhancedcomposite color toner image,

transferring the enhanced composite color toner image to a receivermaterial to form a transferred enhanced composite color toner image, and

fixing the transferred enhanced composite color toner image to thereceiver material,

-   -   wherein each visible fluorescing magenta toner particle consists        essentially of a polymeric binder phase and a visible        fluorescing colorant that emits at one or more peak wavelengths        of at least 510 nm and up to and including 590 nm and that is        dispersed within the polymeric binder phase.

2. The method of embodiment 1, wherein the covering power of the visiblefluorescing magenta toner particles in the transferred enhancedcomposite color toner image is at least 350 cm²/g to and including 1100cm²/g, and the covering power of each of the non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner particles in the transferred enhanced composite color tonerimage is at least 1500 cm²/g to and including 2300 cm²/g.

3. The method of embodiment 1 or 2, wherein the covering power of thevisible fluorescing magenta toner particles in the transferred enhancedcomposite color toner image is at least 400 cm²/g to and including 600cm²/g, and the covering power of each of the non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner particles in the transferred enhanced composite color tonerimage is at least 1700 cm²/g to and including 2100 cm²/g.

4. The method of any of embodiments 1 to 3, wherein the visiblefluorescing magenta toner particles comprise a rhodamine classfluorescing colorant that emits at one or more peak wavelengths of atleast 520 nm and up to and including 590 nm, that is present in anamount of at least 0.5 weight % and up to and including 10 weight %,based on the total visible fluorescing magenta toner particle weight.

5. The method of any of embodiments 1 to 4, wherein the visiblefluorescing magenta toner particles have a mean volume weighted diameter(D_(vol)) before fixing of at least 4 μm and up to and including 20 μm.

6. The method of any of embodiments 1 to 5, wherein the visiblefluorescing magenta toner particles have a mean volume weighted diameter(D_(vol)) before fixing of at least 5 μm and up to and including 12 μm.

7. The method of any of embodiments 1 to 6, wherein the visiblefluorescing magenta toner particles further comprise a charge controlagent, wax, lubricant, fuser release aid, or any combination of thesematerials.

8. The method of any of embodiments 1 to 7, wherein the visiblefluorescing magenta toner particles further comprise, on their outersurface, a fuser release aid, flow additive particles, or both of thesematerials.

9. The method of any of embodiments 1 to 8, wherein the receivermaterial is a sheet of paper or a polymeric film.

10. The method of any of embodiments 1 to 9, comprising formingnon-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta,non-fluorescing black, and visible fluorescing magenta developed tonerimages on the receiver material using at least five sequential tonerstations in a color electrophotographic printing machine, whichsequential toner stations are equipped with the non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, non-fluorescing black,and visible fluorescing magenta toner particles, respectively.

11. A printed receiver material provided by the method of any ofembodiments 1 to 10, comprising a printed enhanced composite color tonerimage comprising fused visible fluorescing magenta toner particles thatprovide a fluorescing magenta effect printed over non-fluorescing cyan,non-fluorescing yellow, non-fluorescing magenta, and non-fluorescingblack toner images in the printed enhanced composite color toner image.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner.

Dry toner particles were prepared using a polymeric binder resinsparticles that were melt processed in a two roll mill or extruder withappropriate colorants and addenda. A preformed mechanical blend ofparticulate polymer resin particles, colorants, and toner additives canalso be prepared and then roll milled or extruded. Roll milling,extrusion, or other melt processing was performed at a temperaturesufficient to achieve a uniform melt processed composition. Thiscomposition, referred to as a “melt product” or “melt slab” was thencooled to room temperature. For a polymeric binder having a T_(g) in therange of from 50° C. to 120° C., or a T_(m) in the range of from 65° C.to 200° C., a melt blending temperature of from 90° C. to 240° C. wassuitable using a roll mill or extruder. The melt blending times (thatis, the exposure period for melt blending at elevated temperature) wasin the range of from 1 minute to 60 minutes.

The components were dry powder blended in a 40 liter Henschel mixer for60 seconds at 1000 RPM to produce a homogeneous dry blend that was thenmelt compounded in a twin screw co-rotating extruder to melt the polymerbinder and disperse the pigments, charge agents, and waxes uniformlywithin the resulting polymeric binder phase. Melt compounding was doneat a temperature of 110° C. at the extruder inlet, increasing to 196° C.in the extruder compounding zones, and 196° C. at the extruder dieoutlet. The melt extrusion conditions were a powder blend feed rate of10 kg/hr and an extruder screw speed of 490 RPM. The extrudedcomposition (extrudate) was cooled to room temperature and then brokeninto about 0.32 cm size granules.

These granules were then finely ground in an air jet mill to a D_(vol)of 8 μm as determined using a Coulter Counter Multisizer. The finelyground toner particles were then classified in a centrifugal airclassifier to remove very small particles and fines that were notdesired in the finished dry toner composition. After classification, thetoner particles had a particle size distribution with a width, expressedas the diameter at the 50% percentile/diameter at the 16% percentile ofthe cumulative particle number versus particle diameter, of 1.30 to1.35.

The classified toner particles were then surface treated with fumedhydrophobic silica (Aerosil® R972 from Nippon Aerosil) wherein 2000grams of toner particles were mixed with 20 grams of the fumedhydrophobic silica so that 1 weight % silica was attached to the tonerparticles, based on total toner particle weight using a 10 literHenschel mixer with a 3-element impeller for 2 minutes at 2000 RPM.

The silica surface-treated toner particles were sieved using a 300 meshvibratory sieve to remove non-dispersed silica agglomerates and anytoner particle flakes that may have formed during the surface treatmentprocess.

The melt extrusion composition was cooled and then pulverized to aD_(vol) of from about 5 μm to about 20 μm. It is generally preferred tofirst grind the melt extrusion composition prior to a specificpulverizing operation using any convenient grinding procedure. Forexample, the solid melt extrusion composition can be crushed and thenground using, for example, a fluid energy or jet mill, such as describedin U.S. Pat. No. 4,089,472 (noted above) and the ground particles canthen be classified in one or more steps. If necessary, the size of theparticles can be further reduced by use of a high shear pulverizingdevice such as a fluid energy mill and classified again.

Two-component electrographic developers were prepared by mixing tonerparticles prepared as described above with hard magnetic ferrite carrierparticles coated with silicone resin as a concentration of 8 weight %toner particles and 92 weight % carrier particles.

Invention Example 1

A visible fluorescing magenta (pink) dry toner formulation was made with12,000 g of Reichhold Atlac 382 ES polyester resin, 2200 g of DaygloWRT-11 Aquabest Pink visible magenta fluorescing colorant, and 293 g ofOrient Bontron E-84 charge control agent.

These components were dry blended using a 40 liter Henschel mixer for 60seconds at 1000 RPM to produce a homogeneous dry blend. The dry blendwas then melt compounded in a twin screw co-rotating extruder to meltthe polymer binder and disperse the fluorescing colorants, and chargecontrol agent at a temperature of 110° C. at the extruder inlet, 110° C.increasing to 196° C. in the extruder compounding zones, and 196° C. atthe extruder die outlet. The processing conditions were a powder blendfeed rate of 10 kg/hr and an extruder screw speed of 490 RPM. The cooledextrudate was then chopped to approximately 0.32 cm size granules.

These granules were then finely ground in an air jet mill to an 8 μmD_(vol) as measured using a Coulter Counter Multisizer. The finelyground toner particles were then classified in a centrifugal airclassifier to remove very small toner particles and toner fines that arenot desired. After this classification, the visible fluorescing magentatoner product had a particle size distribution with a width, expressedas the diameter at the 50% percentile/diameter at the 16% percentile ofthe cumulative particle number versus D_(vol) of 1.30 to 1.35.

The classified toner was then surface treated with fumed silica, ahydrophobic silica (Aerosil® R972 manufactured by Nippon Aerosil) bymixing 2000 g of the visible fluorescing magenta dry toner particleswith 20 g of the silica to give a dry toner product containing 1.0weight % silica in a 10 liter Henschel mixer with a 4 element impellerfor 2.5 minutes at 3000 RPM. The silica surface-treated visiblefluorescing magenta toner particles were sieved through a 300 meshvibratory sieve to remove non-dispersed silica agglomerates and anytoner flakes that may have formed during the surface treatment process.

The covering power of the visible fluorescing magenta (pink) tonerparticles was measured at 400 cm²/g in the resulting printed enhancedcomposite color toner images. A two-component dry developer was preparedby combining 100 g of the noted toner particles with 1200 g of carrierparticles comprising strontium ferrite cores that had been coated at230° C. with 0.75 parts of poly(vinylidene fluoride) (Kynar™ 301Fmanufactured by Pennwalt Corporation) and 0.50 parts of poly(methylmethacrylate) (Soken 1101 distributed by Esprix Chemicals).

The two-component dry developer were then used in the fifth printingstation (toner imaging unit) of a NexPress™ 3000 Digital Color PrintingPress containing non-fluorescing cyan, non-fluorescing magenta,non-fluorescing yellow, and non-fluorescing black toner particles in thefirst four printing stations. After application of the various tonerparticles to paper sheets as the receiver material, and fixing, thecovering power for these non-fluorescing color toners was measured at1650 cm²/g, 1700 cm²/g, 2200 cm²/g, and 1800 cm²/g respectively, in theresulting printed enhanced color toner images.

It was evident that the presence of the visible fluorescing magentatoner particles in the enhanced color toner images provided a “pinkish”effect to the color toner image. This fluorescing effect can be variedby using variations of amounts of fluorescing and non-fluorescing tonerparticles, visible fluorescing colorant, and other features that aredescribed above.

Invention Example 2

Using visible fluorescing magenta dry toner particles in the fifthprinting station, various toner images were printed on a NexPress™ 3000Digital Color printing press that was equipped with standardnon-fluorescing CYMK toners in the first four printing stations. Whencompared with the standard 4-color image, the addition of the visiblefluorescing magenta toner image (fluorescing “pink” hue) provided morewarm hue and colorfulness to the human skin tones in the toner images.Color properties of the various skin tones produced with 4 and 5-colorprocess were measured by a Gretag Spectrolino Spectrophotometer and aresummarized below in TABLE I. The data show that the 5-color imagesproduced differences in the human skin tones as well as the chroma atthe same print density of the human skin tones. In general, the 4-colorimages had a more blue skin tone hue. When there were no other imagesavailable to compare against, the 4-color images appeared acceptable.But when the 4-color image was compared against the 5-color imagesproduced according to the present invention, blue hue seen in the humanskin tones was objectionable. When these images were shown randomly toseveral people, all of the observers preferred the warmer hue in thehuman skin tones that were produced according to the present invention.

In TABLE I, L*, a*, and b* parameters are known CIEL*a*b* color scaledesignations that are known in the art for example from the CEI 1976standards. In colorimetry or color theory, “chroma” is known as the“colorfulness”, color saturation, or perceived intensity of a givencolor. More details of such property can be found in the book by R. W.G. Hunt, Measuring Color, 2^(nd) Ed. page 32 (similar details can befound in later editions by the same author).

TABLE I Image Toner Image Colors Density L* a* b* Chroma CYMK 0.22 87.265.04 9.11 10.41 CYMK + Visible 0.22 87.14 7.71 8.88 11.76 FluorescingMagenta CYMK 0.42 78.49 10.61 18.11 20.99 CYMK + Visible 0.41 78.0114.29 16.14 21.55 Fluorescing Magenta CYMK 0.60 67.51 14.74 17.55 20.86CYMK + Visible 0.61 67.46 14.99 14.5 22.92 Fluorescing Magenta CYMK 0.8269.02 15.03 36.57 36.91 CYMK + Visible 0.85 64.01 20.61 30.62 39.54Fluorescing Magenta CYMK 1.16 56.15 49.41 41.0 64.21 CYMK + Visible 1.2858.52 53.27 50.74 73.57 Fluorescing Magenta

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

The invention claimed is:
 1. A printed receiver material provided by a method comprising: forming one or more latent images, developing the one or more latent images with non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles, in any desired sequence, to form a composite non-fluorescing color toner image, developing visible fluorescing magenta dry toner particles in close proximity with the composite non-fluorescing color toner image to provide an enhanced composite color toner image, transferring the enhanced composite color toner image to a receiver material to form a transferred enhanced composite color toner image, and fixing the transferred enhanced composite color toner image to the receiver material to form a printed receiver material comprising the receiver material as a substrate and having thereon, the enhanced composite color toner image comprising fused visible fluorescing magenta toner particles that provide a fluorescing magenta effect printed over non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner images in the enhanced composite color toner image that has a higher chroma image, wherein each visible fluorescing magenta dry toner particle consists essentially of a polymeric binder phase and a visible fluorescing colorant that emits at one or more peak wavelengths of at least 510 nm and up to and including 590 nm and that is dispersed within the polymeric binder phase, and wherein the covering power of the fused visible fluorescing magenta toner particles in the enhanced composite color toner image is at least 350 cm²/g to and including 1100 cm²/g, and the covering power of each of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles in the enhanced composite color toner image is at least 1500 cm²/g to and including 2300 cm²/g.
 2. The printed receiver material of claim 1, wherein the covering power of the fused visible fluorescing magenta toner particles in the enhanced composite color toner image is at least 400 cm²/g to and including 600 cm²/g, and the covering power of each of the non-fluorescing cyan, non-fluorescing yellow, non-fluorescing magenta, and non-fluorescing black toner particles in the enhanced composite color toner image is at least 1700 cm²/g to and including 2100 cm²/g.
 3. The printed receiver material of claim 1, wherein the fused visible fluorescing magenta toner particles comprise a rhodamine class fluorescing colorant that has one or more peak wavelengths of at least 520 nm and up to and including 590 nm, that is present in an amount of at least 0.5 weight % and up to and including 10 weight %, based on the total visible fluorescing magenta dry toner particle weight.
 4. The printed receiver material of claim 1, wherein the visible fluorescing magenta dry toner particles have a mean volume weighted diameter (D_(vol)) before fixing of at least 4 μm and up to and including 20 μm.
 5. The printed receiver material of claim 1, wherein the visible fluorescing magenta dry toner particles have a mean volume weighted diameter (D_(vol)) before fixing of at least 5 μm and up to and including 12 μm.
 6. The printed receiver material of claim 1, wherein the substrate comprises a coated or uncoated paper, ceramic, paperboard, cardboard, metal fibrous web or ribbon, or polymeric film, on which the enhanced composite color toner image is fixed.
 7. The printed receiver material of claim 1, wherein the substrate comprises a cellulosic receiver material containing a blue dye or optical brightener, on which the enhanced composite color toner image is fixed.
 8. The printed receiver material of claim 1, wherein the enhanced composite color toner image has a higher chroma of at least 7% compared to the composite non-fluorescing color toner image at the same image density.
 9. The printed receiver material of claim 1, wherein the enhanced composite color toner image has a higher chroma of at least 9% compared to the composite non-fluorescing color toner image at the same image density. 